This kind of plant cultivating device has been invented by the applicant. For example, in the Japanese Unexamined Patent Publication No. 245646/1994, a multistory work bench as a plant cultivating device is disclosed. The bench has a number of trays hanged by a chain conveyor circulating in a building, wherein the cultivating process of plants is so automated that only supply and retrieval of trays to and from the conveyor is done by workers, seedlings being planted in the trays. And in the Japanese Unexamined Patent Publication No. 136790/1998, a cultivating shelf is disclosed. The shelf employs a fixed shelf frame, a cultivating vessel placed on the shelf frame, and a light source equipped with light-emitting diodes etc. located over the each vessel. Further, in the Japanese Unexamined Patent Publication No. 106757/2000, another plant cultivating device is disclosed. The device employs a plurality of conveyors above and below, up and down mechanism for supply and retrieval located at each input side and output side of the conveyor.
The multistory work bench type plant cultivating device has complicated drive mechanisms and requires complex supporting methods. Since the trays are aligned with relatively large intervals, the spaces between trays are useless when the plants are in their stage of being seeds or seedling. The useless spaces require longer water-supply pipes and also cause low illumination efficiency due to longer intervals between the light sources. In the cultivating shelf, it is possible to move the vessel to a larger shelf depending on the growth of the plants, but it involves great difficulties. In the Japanese Unexamined Patent Publication No. 106757/2000, a particularly large space is required in the grown stage of the plants causing insufficient efficiency of the illumination.
It is known in the field of hothouse cultivation of vegetables to employ lighting devices such as fluorescent lamps for illuminating the plants in order to get the effects similar to prolonged daylights. Particularly in industrial cultivation of vegetables, the cultivating vessels are placed on the several tiered shelf and illuminated by lighting devices to secure sufficient cultivating area.
In this case, it is disclosed to use a lighting-emitting panel on which a number of light-emitting diodes (LED) are arranged as a lighting device for the illumination of plants (for reference: the Japanese Unexamined Patent Publication No. 275779/1997 etc.). Such a lighting panel comprises a circuit pattern formed on a aluminum board, and a number of LED arranged on the circuit pattern, the LED being enclosed on the pattern using a translucent synthetic resin, wherein a reflecting plate is sometimes inserted between the LED and the board in order to increase light volume.
Conventional lighting devices such as fluorescent lamps consume a large amount of electric power causing high electricity charges, and their large amount of heat emission requires a measurable amount of power consumption in the air conditioners. On the other hand, the lighting panel using LED has a problem that it has no advantage over the fluorescent lamps in the durability because of probable degradation in high environmental humidity. Further, it has other problems that in the case of using large number of LED the manufacturing process takes a great deal of labor, and that the light volume of the panel is insufficient. The process is as follows: a LED is soldered on the circuit pattern formed on the base, an electrode is soldered on the circuit pattern, the LED and the electrode are bonded using a gold wire, and then a metal mold is mounted on the circuit pattern into which melted translucent synthetic resin such as epoxy resin is poured to enclose them within the mold. In the case that a reflecting plate is employed, the LED is soldered on the dish reflecting plate first, and then soldered on the circuit pattern of the base, wire bonded, and finally enclosed with the resin.
The present invention is directed to save the useless space and to increase the lighting efficiency of the conventional plant cultivating devices, and also directed to provide a lighting panel having the feature of low electric power consumption, low heat emission, and high durability. In addition, another object of the invention is to provide a lighting panel having large light volume and easy to manufacture.